Typically, hard disk drives (HDDs) are sealed to prevent contaminants from entering the HDD and/or prevent gas within the HDD from escaping. There can be about fifteen non-hermetic seals, all of which use polymers (e.g., elastomer gaskets and adhesive tape). Also, a breather filter is utilized to equalize interior pressure with exterior pressure. Unfortunately, a true hermetic seal can not be established using traditional sealing methods. Accordingly, a high permeation rate of gas can result. For example, the solubility of water vapor and diffusion coefficients of a low-density gas (e.g., helium) are very high.
Moreover, a traditional die-cast aluminum base plate may be too porous to contain a low-density gas for the lifetime of the HDD. Also, with aluminum-to-aluminum and aluminum-to-steel hermetic joining, it is difficult and expensive to create a true hermetic seal.
The drawings referred to in this description should be understood as not being drawn to scale except if specifically noted.